1. Field of the Invention
The present invention relates to a cleaning system and cleaning method of decomposing dioxins contained in a contaminated matter which comprises the dioxins using crushed cells or fractions thereof of microorganisms in an aqueous medium and a preparation for decomposing dioxins, which is used for cleaning of the contaminated matter.
2. Description of the Related Art
Operation or supervision of facilities which emit dioxins such as incinerators has been regulated by law at present, and emission of dioxins is prevented. However, existing facilities which do not meet the standards of the law require operations such as dismantling and improvement. In such an operation, a contaminated matter containing dioxins generates in various forms. A technique for decomposing dioxins by using microorganisms is known as a preferable technique for cleaning a contaminated matter by decomposing dioxins in the contaminated matter.
Examples of a known technique for decomposing dioxins by using microorganisms include a method for treating a liquid containing dioxins (see JP 2002-028695 A, for example). The method includes at least: a primary step of trapping dioxins in a liquid containing dioxins by adsorption or sorption of the dioxins to a solid and concentrating; a secondary step of subjecting the treated liquid containing the solid with concentrated dioxins to solid-liquid separation for obtaining dioxin-free separated water and concentrated slurry; and a tertiary step of subjecting the concentrated slurry to biological treatment for decomposing the dioxins in the concentrated slurry. The biological treatment in the tertiary step employs a wood-rotting fungi and/or an enzyme in which the wood-rotting fungus produces.
Further examples of the known technique for decomposing the dioxins by using microorganisms include a demolishing method of structure polluted with dioxins (see JP 2001-090353 A, for example). The method is characterized by including: secluding an incinerator facility contaminated with dioxins from a surrounding environment; allowing a composition containing a microorganism having an ability of decomposing dioxins and containing a coat forming immobilizing agent to adhere to inner walls of the incineration facility; and demolishing the incineration facility. A wood-rotting fungus such as a white-rot fungus of Basidiomycetes is used as a preferable microorganism.
Further, Bacillus midousuji is known as a microorganism for decomposing dioxins (see Sadayori Hoshina et al., “Decomposition experiment of dioxins by thermophile and gene analysis”, Collected Papers II from 10th Annual Conference of The Japan Society of Waste Management Experts, The Japan Society of Waste Management Experts, p. 883-885, 10.10.1999, for example), and a method for cleaning a contaminated matter using Bacillus midousuji is known (see JP 2002-301466 A, for example).
However, in the conventional techniques, decomposition activities of the fungus or produced enzymes thereby may be lost with dioxins having three or more chlorine atoms depending on the fungus or the enzymes thereby used. The loss of the decomposition activities probably results from inactivation of enzymes produced by fungus, which cannot act on dioxin decomposition such as dechlorination due to steric hindrance of chlorine atoms bonded to skeleton structures of dioxins.
Further, handling of the contaminated matter containing dioxins has been also now stipulated by law in detail recently. Thus, dioxins are desirably decomposed at sites in which the contaminated matter generates without transporting the contaminated matter to facilities such as treatment plants. However, decomposition of dioxins by using fungus at a site in which the contaminated matter generates requires the formation of an environment allowing the fungus to survive at the site in which the contaminated matter generates or during the contaminated matter is cleaning (adjustment of temperature, pH, or salt concentration, use of medium, and the like). Consideration on simplification or efficiency improvement of the cleaning system is still needed.